Tech

3-D Printed Ceramics Could Build Next-Gen Spaceships

Researchers have used a 3-D printer to make customized ceramic parts that have also overcome the Achilles’ heel of ceramic objects: their tendency to crack. Could it be used in the design of spacecraft?

Engineers have always liked ceramic parts -- they are strong, lightweight and handle heat better than many metals, ideal for crafting parts for airplanes or rockets. Heat-shielding tiles on the space shuttle were made from ceramics, for example.

Now researchers have used a 3-D printer to make customized ceramic parts that have also overcome the Achilles' heel of ceramic objects: their tendency to crack.

The finding could open the door to a new class of ceramic-body or ceramic-engine jets, perhaps even a hypersonic craft that can fly from New York to Tokyo in a few hours.

"If you go very fast, about 10 times speed of sound within the atmosphere, then any vehicle will heat up tremendously because of air friction," said Tobias Schaedler, senior scientist at HRL Laboratories in Malibu, Calif. "People want to build hypersonic vehicles and you need ceramics for the whole shell of the vehicle."

Schaedler and colleagues at HRL invented a resin formulation that can be 3-D printed into parts of virtually any shape and size.

The printed resin can then be fired, converting it into a high strength, fully dense ceramic. The resulting material can withstand ultrahigh temperatures in excess of 1,700 degrees Celsius (3,092 Fahrenheit) and is 10 times stronger than similar materials.

Ceramics are much more difficult to work with than plastics or metals because they cannot be cast or machined easily, according to Schaedler, who is an author on the new study appearing today in the journal Science.

But Schaedler's team figured out how to trick ceramics into behaving like plastic.

"We have a pre-ceramic resin that you can print like a polymer, then you fire the polymer and it converts to a ceramic," he said. "There is some shrinkage involved, but it's very uniform so you can predict it."

The big picture is that this method could help rocket and satellite designers who have to make lots of special small parts that are capable of resisting the heating that occurs during high velocity air friction, as well as high temperatures generated by the exhaust during takeoff.

A form of ceramic called alumina is being used in new ion propulsion drive, which uses electricity to heat gas and generate ions, according to Charlie Spahr, executive director of the American Ceramics Council.

"Ceramics are really good where you want to reduce wear and tear," Spahr said.

The Pentagon's research branch has been funding various projects to discover new ways to build lighter, stronger and more heat-resistant materials for aerospace and military applications.

"The method described in the new Science paper brings us closer to the goal of being able to 'engineer in' desired material properties that generally are not found together, such as strength and low density or low weight, and to craft these materials into complex shapes," said Stefanie Tompkins, director of the Defense Science Office at the Defense Advanced Research Projects Agency (DARPA).

Figuring out how to make customized 3-D printed ceramic parts could also make a difference in gas-fired power plants, for example, or other types of gas engines, according to DARPA officials.

With crews of three to six people to support, the International Space Station (ISS) has a tough job that it can't do all on its own. The facility depends on regular resupplies from Earth to carry food, water and equipment for the astronauts on board -- not to mention all the science experiments.

However, in the past year, three separate programs have suffered failures to their resupply programs. But overall, the track record of the program has kept the ISS flying with people continuously since November 2000. On Wednesday (Aug. 19), the Japanese Space Agency (JAXA) launched their H-II Transfer Vehicle (HTV) on a 5-day mission to the ISS.

Let's take a tour of the space station's fleet of private and government-run resupply spaceships.

There were five European Automated Transfer Vehicles (ATVs) that carried supplies to orbit. They were capable of carrying dry cargo (such as hardware) and fluid cargo (such as station fuel) inside for transfer for the station. The pressurized section, which made up 90 percent of the cargo carrier, could be accessed by two astronauts for up to eight hours to allow ample time for unloading. The last ATV departed the station in February 2015 and broke up as planned in the atmosphere, laden with sensors. The intention is to design better cargo spacecraft in the future, ESA said at the time.

Cygnus is a spacecraft developed by private company Orbital Sciences Inc. under a Commercial Orbital Transportation Services contract from NASA. The spacecraft has made four attempts to reach the International Space Station since September 2013; the latest one, in October 2014, ended in an explosion due to a problem with the rocket that was carrying it. Cygnus "borrows" from the design of other products Orbital has created for spaceflight. For example, the service module has avionics, propulsion and power systems used in GEOStar communication satellites.

Like Cygnus, Dragon was also developed using NASA funding from the Commercial Orbital Transportation Services program. Out of nine resupply runs to the station, Dragon has made it safely all but once (in its latest attempt in June, due to a rocket failure.) The spacecraft can carry sensitive biological experiments such as mice or blood samples. It was the first to dock with the space station in 2012. SpaceX is now using a similar design to create a human-rated spacecraft that would fly no earlier than 2017.

The H-II Transfer Vehicle (HTV) -- also known as Kounatori, which means "white stork" -- has now launched five times to the International Space Station since 2009. The fifth HTV cargo run is currently in progress having launched on Wednesday (Aug. 19) and due to arrive at the space station on Monday (Aug. 24).

The spacecraft includes a pressurized internal section for crew cargo or experiments, and an exposed pallet that carries experiments or spare parts to be mounted outside of station using the Kibo robotic arm. While the current HTV mission is the final launch under the JAXA-NASA agreement, NASA spokesperson Stephanie Schierholz told Discovery News that the agencies will add at least two more HTV flights -- more are possible as well.

Progress is by far the longest-running workhorse of space station cargo ships. Versions of the spacecraft have been in use in space since 1978. The Progress-M spacecraft has made nearly 60 flights to the ISS, carrying dry cargo as well as fuel to the orbiting complex. In recent years, a Progress was lost in 2011 due to a launch failure. Earlier this year, a Progress made it to orbit but could not be controlled to direct it to the station.

The space shuttle wasn't only a space station cargo ship, it also played a leading role in

constructing

the International Space Station. Crews of up to seven people could be accommodated in its cabin while not losing any space for cargo, which would ride in the back payload bay. Some of the major parts of the station hauled to orbit include the Unity Node (the first U.S. part of the station), the Cupola viewing windows, the Joint Airlock and the robotic Canadarm2 that is used to assist astronauts during spacewalks. The shuttle was retired in 2011.